Intersection table representing the resolution of a many to many relationship.

activity_s (FSK, M: CHAR VARYING(19))
activity_t (M: CHAR VARYING(16))
contractual_obl_s (FSK, M: CHAR VARYING(19))

contractual_obligation.contractual_obligation_activity
This contractual obligation may be satisfied by one or more instances of activity.
activity.contractual_obligation
This instance of an activity satisfies the contractual obligation.
activity_s: Implements a foreign key to a row in one of the tables projected from entity activity depending on the value of the next column (See below).
activity_t: Defines the name of the referenced table. Possible values are defined in @activity.
contractual_obl_s: Defines a foreign key to table contractual_obl.